1. Field of the Invention
The present invention relates to a magnetic recording and reproducing apparatus and a magnetic recording and reproducing method thereof in which one frame consists of tracks the number of which is a multiple of an even number and the data processing in recording and reproducing is performed in a frame unit, and more particularly to a frame synchronizing method for synchronizing the phase of a reference frame pulse with that of a reproducing frame indicated by a track number in a frame of a reproducing signal in tracking control.
2. Description of the Related Art
Recently, a helical scan type magnetic recording and reproducing apparatus using a magnetic tape as a recording medium has been developed as a data recording and reproducing apparatus of a computer or the like.
Conventionally, in this kind of magnetic recording and reproducing apparatus, one frame consists of tracks the number of which is a multiple of an even number and the data processing in recording and reproducing is performed using a reference frame pulse representing a frame unit. That is, though recording and reproducing is performed for each track by a recording and reproducing head based on the reference frame pulse to the magnetic tape, the data processing of recording and reproducing is executed in a frame unit.
Therefore, for example, suppose one frame consists of ten tracks, the tracks (track numbers 0 through 10) of a frame reproduced by a magnetic head should be arranged in order from the head of the reference frame pulse generated in the magnetic recording and reproducing apparatus in reproducing, that is, the track number of the reproducing frame should be synchronized with the phase of the reference frame pulse. If the phase of the reproducing frame is not synchronized with that of the reference frame, it will be impossible to reproduce data.
Conventionally, this kind of frame synchronizing method that synchronizes the phase of the reproducing frame with that of the reference frame, as the magnetic recording and reproducing apparatus shown in Japanese Published Unexamined Patent Application No. Heisei 4-285746, includes detecting the recorded track information (the track number of the reproducing frame) by executing usual tracking control first, and as a result, if the phase of the reproducing frame were different from that of the reference frame, tape feeding is accelerated or decelerated forcedly according to the difference between the phases to synchronize the phase of the reproducing frame with that of the reference frame after destroying tracking once.
FIGS. 7 and 8 are examples of timing charts explaining a frame synchronizing method according to prior examples.
FIG. 7 shows a relation between the phase of the reference frame pulse and that of the recording track in recording. FIG. 7(A) shows a reference frame pulse in recording. FIG. 7(B) shows a track with track numbers in recording. In recording, the track is recorded in order from the head of the reference frame pulses (for example, at a point of rising) by giving track numbers 0 through 9.
FIG. 8 shows a frame synchronizing method in reproducing. FIG. 8(A) shows a reference frame pulse in reproducing. FIG. 8(B) shows one example of a reproducing track that is actually reproduced. FIG. 8(C) shows a reproducing track having a correct phase with respect to a reference frame pulse. FIG. 8(D) shows on and off of capstan operation (that is, tape feeding operation) controlled for synchronization in the case of reproducing tracks of FIG. 8(B).
In the reproducing frame (the reproducing track) as shown in FIG. 8(B), for example, it is supposed that the tracking control operation is started for a period before an arrow a, tracking is locked (that is, the reproducing head is tracked at the center of the reproducing track) and the track number 2 is detected from the reproducing frame at the point of a (that is, at the point of falling of the reference frame pulse). If the position of tracking at this point of time is a phase in which the fourth track is actually on the reproducing frame under the correct relation of the phase as shown in FIG. 8(C) to the reference frame pulse as shown in FIG. 8(A), it is possible to synchronize the reproducing frame shown in FIG. 8(B) with the reference frame pulse shown in FIG. 8(A) by stopping the capstan as shown in FIG. 8(D) (capstan off) at this position to stop running a tape once, then, by continuing stopping running the tape up to the phase in which the detected second track originally comes to the reference frame pulse as shown in FIG. 8(A), and by running the tape by rotating the capstan (capstan on) as shown in FIG. 8(D) again when coming to the point of b. That is, the point of a corresponds to the point of falling of the reference frame pulse, and judging from that the control means in the apparatus may stop running the tape for a time corresponding to the eight tracks when the reproducing track number 2 is detected at the point of a, the capstan is turned on after the capstan is turned off up to the point of b that a time corresponding to eight tracks has passed. Thus, the reproducing frame is synchronized with the reference frame. Then, the tracking control is performed and tracking is drawn in.
However, the frame synchronizing method of the above-mentioned conventional magnetic recording and reproducing apparatus takes eight tracks to synchronize the phase after stopping the running of the tape and destroying tracking once as shown in FIG. 8. Eight tracks is a lengthy period of time to wait for synchronization Further, it was necessary to control capstan velocity and tracking from the point of b again. The disadvantages in this process include slow synchronization of the frame, the necessity of reinitiating the tracking and that the rising was slow in reproducing.
As mentioned above, in the conventional frame synchronizing method, in order to synchronize the phase of the reference frame with that of the reproducing frame, tracking was controlled first. Then information such as the recorded track numbers was detected and the phase of the reproducing frame (the reproducing track) was recognized. If the phase of the reproducing frame had been different from that of the reference frame, tape feeding should have been accelerated or decelerated forcedly, tracking drawn in once should be destroyed and the phases of both frames should have been synchronized, and then tracking should have been drawn in again. Therefore, synchronizing the phase of the frames, tracking, and the rising in reproducing took too much time to accomplish.